Simple carbs may increase risk of eye disease

Most of us know the definition of a healthy diet and that it
doesn't include a lot of sugars and other simple carbohydrates like
white flour and rice. And most of know why we should avoid these
simple carbohydrates.

Now there may be a new reason to add to the list: maintaining
eye health.

According to a study conducted by researchers at Tufts
University in Boston, eating a lot of simple carbohydrates that
score highly on the glycemic index increases the risk of developing
age-related macular degeneration.

Age-related macular degeneration is a disease that affects the
macula (part of the retina) and causes loss of central vision. In
general, late-stage AMD affects mostly those 65 and older and is
the leading cause of blindness in that age group.

The glycemic index is a scale that classifies
carbohydrate-containing foods according to how quickly they raise
blood sugar levels. For instance, white rice, white bread and
sweets are high-glycemic foods and raise blood sugar quickly (not
good). Foods that score low on the glycemic index are complex
carbohydrates like whole grains and vegetables and raise blood
sugar slowly.

Why are high blood sugar levels detrimental to eyes?

The presence of too much blood glucose too quickly may overwhelm
the ability of the eye cells to use the carbohydrates properly,
said Allen Taylor, who was involved in the study. He is the
director of Tufts University's Laboratory for Nutrition and Vision
Research at the Jean Mayer USDA Human Nutrition Research Center on
Aging.

"We actually began studying cataracts (in the lens of the eye)
first," he said. "We were interested in seeing if there was a
relationship between high blood sugar and cataracts (which are
brown). As a biochemist, I know that the brown color is due to a
chemical reaction between sugars and proteins. Then we thought
maybe some of the chemistry was the same with the retina."

Taylor, dentist Chung-Jung Chiu and their researchers used data
gathered from the nearly 4,100 participants (ages 55 to 80) in the
national Age-Related Eye Disease Study. This original study
assessed the effect of high doses of antioxidant vitamins and zinc
on the progression of age-related macular degeneration and
cataracts. Luckily for the Tufts researchers, participants also had
also supplied information about their diets. When this was
analyzed, researchers found that those who ate more
high-glycemic-index foods developed age-related macular
degeneration more often.

"(We found) that if you eat low-glycemic-index foods, you
diminish the risk of getting AMD by 20 percent," Taylor said.

One lesson here: although late-stage age-related macular
degeneration affects people 65 and older, the disease process
probably starts decades earlier. (With new technology,
ophthalmologists are seeing early stage age-related macular
degeneration in people in their 40s and 50s.) It could be that the
progress of the illness may be prevented with the right diet -- and
that's what researchers will study next.

"Now we want to look at the rate of change in people who ate
high-glycemic-index diets," Taylor said. "Did they go from
low-grade AMD to high-grade AMD faster than those who ate a
low-glycemic-index diet? We're opening up a whole new way of
looking at eye disease, and that you can do something about it. Now
people might ask not only what the fat content of food is, but what
the glycemic index is."